Process for treating lubricating oil with solid adsorbents



May 8,1951 NNE G. A. BE 'r1' ErAL 2,552,436 PROCESS FOR TREATING LUBRICATING OIL WITH SOLID ADSORBEINTS Filed Dec. 9, 1947 WL/cw 62a v/A/ v LUBRIQAr/na Alva SOLI/7V? OUTLET `3M/GA GEL 4 TREAT/YG Tomek uJszz/cAT//vc o/L liv/ ET A 7 30m/ENT PAzv-/ALLY w/rHpRAw/v SQL VEA/'7' INLET ,5 5M-ICA -EL 007257* Patented May 8, 1951 UNITEDl STATES PATENT OFFICE PROCESS FOR -TREATING LUBRICATING OIL WITH SOLID ADSORBENTS George A. Bennett, Center Moriches, N. Y., and Stephen F. Perry, Roselle, N. J.,'assignors to Standard Oil Development Company, a corporation of Delaware Application December 9, 1947, Serial No. 790,542 s claims. (c1.` 19e-147) This invention relates to a process and apparatus for treating fluids with solid adsorbents. The invention particularly relates to the treatment of lube oil stocks with silica gel to improve the viscosity index of the lubricating oil. In accordance with the present invention, a critical amount of solvent is employed as a diluting and washing agent for the lube oil-silica gel treatment to get a maximum improvement in the viscosity index of the lubricating oil.

It is known to the art that the viscosity index of lubricating oils may be improved by treatment with a suitable solid adsorbent. For this purpose a wideyariety of adsorbent materials may be used. For example, adsorbent charcoal; adsorbent clay; iullers earth; bentonite; silica gel, or alumina may be employed. However, it is generally recognized that the adsorbent properties of silica gel qualify it as one of the most scient adsorbents for this purpose. The present invention is therefore described particularly as it relates to the use of silica gel.

Various procedures have been developed suitable for treating a lubricating oil with silica gel. The treatment may be carried out batchwise, or continuously. In general it has been found desirable to add a solvent to the lubricating oil in suficient quantities to serve as a diluent in order to alter the viscosity of the lubricating oil suiciently to enable better contact with' the silica gel. A variety of solvents may be employed.

vIn general any solvent of a non-aromatic nature is suitable, such as an aromatic free petroleum fraction within the gasoline boiling range, normal heptane, pentane, or other light parains', naphthenes, a parain-naphthene mixture su'ch as a light virgin naphtha fraction or an alkylate fraction. It has now been discovered that -a 'critical amount of solvent should be employed Ato secure the maximum improvement invthe'visfirst, as stated, is to suitably dilute the lubricating oil, and the second is to serve as a washing agent to partially desorb constituents from A,

the silica gel, thus improving the selectivity fof adsorption attained. It has now been discovered -that for a given adsorbent treat, and for a 'given -quantity of total solvent, the smallest possible quantity of solvent which will give a stirrable mixture of gel, oil and diluent is preferably employed during initial contacting, while a further 4quantity of solvent should preferably be employed subsequently as a washing agent. By employing the minimum amount of solvent as a diluent, followed by the initial separation of treated oil and further treatment of the silica gel with more solvent, the greatest improvement in the viscosity index of lubricating oils is attained.

The data of rIable I shows the effect on which our invention is based. The table shows the improvement in viscosity index which is obtained for a given treat, using a given amount of solvent, n-heptane, in the case Where the solvent is added as a diluent only and in the case where solvent is added both as a diluent and as a washing agent. The oil treated was a dewaxed Panhandle lube distillate having an initial viscosity index of '78.

The data show that with a 220 wt. per cent treat, that is using 2.2 times as much silica gel as lubricating oil being treated, a viscosity index of 107 may be obtained when using a total of 420% solvent partly as initial diluent and partly as supplementary wash. However, when using the entire 420% solvent as diluent, a viscosity index of only 101 was obtained; the comparative improvement for the diluent wash process being 6 points. Similarly at 440 wt. per cent and 660 wt. per cent gel treats an increase of 3 points in viscosity index is shown when employingv a part of the solvent as a washing agent rather than all of the solvent as a diluent. In the tests listed in Table I, when lsolvent was employed as a wash as well as a diluent, the minimum quantity of solvent was employed which would have the effect o1 producing a stirrable mixture. The remainder of the solvent was then used as a washing agent. `The data presented lead to theconclusion that arom'atics adsorbed by silica gel are p .not readily displaced by normal'heptane Wash when this wash is applied after initial separation of the treated lubricating oil. However, in the presence of both normal heptane and all the lube components a greater solvent action is eX- erted on the adsorbedaromatics. It is apparent, therefore, that an optimum method of operation consists of; rst, contacting the silica gel with lubricating oil which has been diluted with the minimum amount of solvent necessary for formation of a suitable slurry; second,1the .most complete possible separation of una'dsorbed oil from the gel; and third, washing Qfthefgelvwith additional solvent.

Our invention relates to-a iprooess Land -appaF ratus whereby the optimum conditions state-d may be attained in the treatment fof lubricating oil with silica gel. The objects and advantages of our invention will be fully appreciated -from'the following description, together with the accomipa/nylug draw-ingsin which:

zFigu-re f1 --diagrammatical-ly represents :a single '.vessel .:adaptationrofgour invention, vand :Figure 2 ,represents -a l two vessel embodiment ofzzour invention.

:It is-preferred to carryfout` the :process of .our invention continuously. -One embodiment Y.of a foontinuous'process `is shown 'intFigure i1. Inzthis Vgnre, 'the numerals! designates-: 'a-eiaertical. treat- .ing tower. At Ythe-top offtower 25,;A-.silica gel-is introduced through line 2 by means of 1a :star

roeden-basket valve i3, or other suitable means for introducing solids into aliquid system. The silica gelgintrocluced at the Ytop 'of the :tower Vfalls ldownwardlythrough 'the tower and is withdrawn at -the bottom I of the V@towcr through lline 1-3 by rmeans of abasketivalve N., Aor other suitable means. Lubricating oil to -be itreatedfisi-ntro- :duced through :line -4 midwayup vthe :tower and fows ,upwardly :through :the ltower countercurrent to the downward flow of the silica gel. The treated lubricating oil may be withdrawn at the top of the tower vthrough line 5. In accordance with the present invention, YaY-suitable solvent isintroduced .through v.line 6 at the bottom fof the tower. This solvent filows upwardly through the `tower and is partially fwithdrawn midway lup the itower through line l. The remainder of the solvent not withdrawn through line il proceeds upwardly through the;tower being removed together with the treated lubricating oil. In order to .suitably .improve Vthe viscosity index of lubricating oils, in general, about ..220 wt. `per ycent Ato .660 wt. :per cent treat, kthat is weightvof gel based on lube oil ftreated, should be employed. Expressing ythis yfigure ,in va different manner .an oil y-to Ygel ratio in the range Aof .about Y,0.5 `to 0.2 .-co. of vvlubricatingoil pergram orgel-should beused. YWhile the exact .value depends to some extent on the yparticular gel .size used, vthe minimum vliquid to `gel ratio .which produces a stirrable slurry is .generally abcutli) to 1.5 cc. per gram. More precisely, V.the .ratio preferred is about .1.2 .to .1.,4 cc. per.gram. For example, in the case of 28..to.200 mesh gehabout 1.3 ccs. of liquid are required per .gram of v.gel to producea stirrable 6 slurry. In accordance withlthis inventiom'therefore, Ysuiicient solvent `should bef present during .treating .ofthe lubricating 'oil to produce a liquid to gel :ratio -in =the above range. To secure effective washing -of desirable ylube components vfrom-.silica gelreouiresabom 1fto125 cc. of wash kfper .grain-of silioagel. Applying these lcritical Iigures Ato .the 4operation of 4the toweinshown iin Figure l, sucient lubricating oil will be introduced through line 4 relative to silica gel introduced through line 2 so that a ratio of oil to gel of about 0.5 to 0.2 ccs. of lube per gram of gel will be obtained. Suicient solvent will be yintroduced through linev .so-thatabout 1 to 1.5 ccs. of wash will be providedfper gram of silica gel. Sufficient solvent will be withdrawn through v.line l so that the solvent and desorbed lube comnponentsproceeding upwardly through the tower together' with the fresh lubricating oil will provide -a liquid -to gel ratio of about 1.0 to 1.5 ccs. :pergram.

z-Sndesorhedwthe embodiment of Figure 1 will be:obserye'drtofcomprise 2 treating zones; a lower treating =zone-having a high ratio of solvent to Slicagel op eljcrtrigv as a wash zone, and an upper zone in which the 'liquid present is the minimum which `will provide a stirrable slurry operating as a primary contacting zone of the lubricating oil .and-silica Infthe upperL-partof ,the tower, thereforer-.sijlicagel is contacted with lubricating oil -which has Ibeen diluted =with the Vminirmnn :amount of :solvent necessary forformation of .a .stirrable slurryselectivelyadsorbing.l rconstituents .of fthe lubricating oi-l. As the silica vgel -falls downwardly throughthe tower, it -passesI .the .in- .let.4:- through whichlubricating loil is introduced 4.s orthat silicagel. passing thispoint ofthe tower, is partially separated etroml-unadsorbedoil. This silica gel falling .into .theflowerpart ofthe-tower is athen washed A'with the :additional solvent, circulatine in the lower ,part of :the :tower through :hueso-:and J.

{Ihe `washing action. which occurs in the vlower part fof vthe ,tower .-has the effect of washing, or desorbing :from Ythe :silica egel, constituents of the .lube-oils lwhich havelbeenadsorbed bythe gel. 'These vconstituents will tend to rise v,upwardly .in v.the y:tower forming a layer Vabove v7the point lat which, the ,solvent-is withdrawn, that is above line 1. The prasence V,of v:these desorbed .constituents of the -ylubricating -oil has the effect of.-increasingtheselectivity Twith' .which the silica gel Vremoves the :constituents-of @the lubricating In\ or der .tofsecure.ahetterv sepa-ration of .unad rscribed/,foil from silica gel itaisfdesirablefto 'usea ftWo .step treating-process, rather V4 tha-n j.the single .tower-of Figure 1. ,-Snch 'ia-*two stepprocess is illustrated ,-in .Figure .2. Referring yto Eigure .'2, the .;iirs tstep ofthefprocess ,-is carriedfout-intower 20. :Silica geliisaintroducedat thetop ottower 20 throughfli-ne 2| employing vsuitable solid vto I-liquid valves. The Asilica gel passesdownwardly through fthe@ tower andgisfremoveds-at the bottom-through line l192. :Lubricating oil is iintroduced at `the bottom ofzthe ytower :through :line .23 and "ows upwardly "through the :tower to be removed through-line 2 4. v'llheluhrica-ting oil Vintroduced through line;: 2f 3:is suitably diluted .with a solvent `introducedthrough:line521|. The quantity of vsolvent:employed together withithe amount of lube .'oilerelative v to rtheramount'of silica gel, is -such -that lthe 'liquidto -gel ratio is the 'minimum atwvhicha stirrable slurry exists. ,The silicagel yreniovedirom-the bottom of the towerthrough --line 2 2 is separatedascompletely fasi possible: into .oil and gel :components in -lter, for I equivalent fmeans-21. The :oil separated may -be recycledito "treating `toys/eri!) bymeansof lline 2'8. The silica 4'gelfgfreed 'of entrained oil is fthen transferred -throughline 29 :to treatingzone 30. The-silica trgelgmay .beprintroduced tovtower :311 at :the top of ithertowerffandamay beallowed tofall downwardly through the tower as in tower 20. A critical K through suitable feed iets.

amount of wash solvent is introducedat the bottom ofthe tower through line 3l and flows upwardly through the tower to be removed'through line 32. A portion of the solvent removed through line 32 may be used as the solvent introduced to tower through line 2li. Constituents of the lube oil desorbed from the silica gel in the wash zone are withdrawn from the top of tower 30, through line 33, are stripped of solvent instill 31. and are returned to tower 20 at the bottom of the tower. The relative proportions of lube oil, silica gel, wash solvent and diluent solvent are adjusted as indicated in connection with Figure l.y It is apparent that the two step process of Figure 2,

is thus equivalent to the embodiment of Figure l,

with the provision of ltering or equivalent means to secure the optimum separation of unadsorbed oil from the silica gel prior to washing of the silica gel.

Any suitable vessels may be employed as the treating zones in the embodiments heretofore described. It is preferred that agitation of the silica gel slurry be obtained by mechanical stirrers, or by the introduction of the diluted lube oil Bafes or other devices for improving or regulating the countercurrent flow may be used. Other engineering renements known to the art may be employed in these towers. It should also be understood that a plurality of vessels arranged in series could be substituted for either or both of the vessels described in Figure 2.

The washed silica gel as obtained from the process described may be further regenerated by additional washing with suitable solvents, by steaming or gas purging at high temperatures, or by controlled combustion. Silica gel regenerated by these methods may then be reintroduced to the treating zones. Similarly solvent which has been employed in the process described may be purified by distillation and may be recycled in the process.

The improved selectivity using the minimum dilution, separation by ltration, and wash procedure illustrated in Figure 2, is demonstrated by the data given in Table II. A series of runsl were made in which the dilution was varied in order to vary the yield obtained, to permit a comparison at equal yields of the procedure in which all solvent used was employed as a diluent and the procedure in which part of the solvent was employed as a wash. The solvent used was n-heptane and the oil treated was dewaxed Panhandle lube distillate having an initial viscosity index of '78.

Table II Minimum Dilu- Dllutlon Only. tion+wash Comparison at- Solvent Total SOL V. l Require- V. I vent Re' inentsl qulre' ments 220 Wt. per cent treat, 52%

yield 103 300 107 420 440 Wt. per cent treat, 58%

yi 106 '770 107 1,000 660 Wt. per cent trent, 48%

yield 109 9.50 111 1, 200

1 Vol. per cont based on lube.

It may be observed from Table II that for a 220 wt. per cent treat, for example, in obtaining a 52% yield, 300 wt. per cent solvent is required when all of the solvent is employed as a diluent,

while L1Z0-wt. per cent solvent is required when that portion of the solvent above the' quantity 'required to get a slurry is employed as. awash.

solvent requirement shown for the minimum dilution plus wash technique, is actually lower in terms of stripping requirements and constitutes an advantage of this process.

As described, this invention comprises the 0ptimum manner of utilizing a given quantity of solvent for a given silica gel-lube oil treat. In accordance with the present invention, only sufcient solvent is employed in the initial silica gellube oil contacting to provide a slurry of the lubricating oil. After an initial separation of unadsorbed lube components the remainder of the solvent is then employed as a wash. This procedure allows the silica gel to exert increased selectivity with the result that a greater improvement in the viscosity index of lubricating oils may be attained.

Having now described this invention, what is claimed is:

1. A process for treating lubricating oils with silica gel in a vertical treating zone in which silica gel is introduced at the top of said zone and drops downwardly through the zone to be withdrawn at the bottom, lubricating oil is introduced midway up the zone, ows upwardly through the zone to be withdrawn at the top, the ratio of lubricating oil to silica gel in the zone being in the range of about 0.2 to 0.5 ccs. per gram, from 1.0 to 1.5 ccs. of a low molecular weight paraflinic hydrocarbon liquid per gram of silica gel is introduced at the bottom of the Zone, flows upwardly through the zone and is partially withdrawn midway up the zone, the remainder being withdrawn at the top of the zone, whereby the total amount of liquid remaining in the upper portion of the zone is that quantity required to form a stirrable slurry with the silica gel falling in the range of about 1.0 to 1.5 ccs. per gram.

2. The process dened by claim 1 in which the said paraiiinic hydrocarbon liquid employed is an alkylate fraction.

3. The process dened by claim 1 in which the said parafnic hydrocarbon liquid employed is an aromatic-free petroleum fraction boiling within the gasoline boiling range.

4. A two Step process for treating lubricating oils with silica gel comprising a first step in which the silica gel is contacted with lubricating oil which is diluted with a low molecular weight parafnic hydrocarbon liquid present in sufcient quantities to form a stirrable slurry, the ratio of the lubricating oil to silica gel being about 0.2 to 0.5 ccs. per gram, and the ratio of the total liquid to silica gel being about 1.0 to 1.5 ccs. per gram, silica gel being removed from the first step, nltered and introduced to the second step in which the silica gel is washed with about 1.0 to 1.5 ccs. per gram of a low molecular weight parafiinic hydrocarbon liquid of the composition employed in the rst step whereby constituents are desorbed from the silica gel, withdrawing said desorbed constituents and recycling them to the first step of the process.

5. The process defined by claim 4 in which the "7 said paranic hydrocarbon liquid nerxmloyed is anlkylate fratinn- 6. The process dened by lolam 4in which'the said ,parafnic hydrocarbon liquid employed is an .aromatic-free petroleum fration boiling within the gasoline boiling range.

GEORGE A. BENNETT. STEPHEN F. PERRY.

'REFERENCES CITED Nllnber 8 UNITED ySTATES PATENTS ,Name .Date

Kearby Sept. 4, 1945 Mavity Feb. 26, 1946 Lipkin Apr. 9, 1946 Walter etal.V Feb. 4, 194'? Hirschler etal May 1 8, 1948 Lpkin et al. Sept. 14, 1948 Hiatt et al. Mar. 15, '1949 

1. A PROCESS FOR TREATING LUBRICATING OILS WITH SILICA GEL IN A VERTICAL TREATING ZONE IN WHICH SILICA GEL IS INTRODUCED AT THE TOP OF SAID ZONE AND DROPS DOWNDARDLY THROUGH THE ZONE TO BE WITHDRAWN AT THE BOTTOM, LURICATING OIL IS INTRODUCED MIDWAY UP THE ZONE, FLOWS UPWARDLY THROUGH THE ZONE TO BE WITHDRAWN AT THE TOP THE RATIO OF LUBRICATING OIL TO SILICA GEL IN THE ZONE BEING IN THE RANGE OF ABOUT 0.2 TO 0.5 CCS. PER GRAM, FROM 1.0 TO 1.5 CCS. OF A LOW MOLECULAR WEIGHT PARAFFINIC HYDROCARBON LIQUID PER GRAM OF SILICA GEL IS INTRODUCED AT THE BOTTOM OF THE ZONE FLOWS UPWARDLY THROUGH THE ZONE AND IS PARTIALLY WITHDRAWN MIDWAY UP THE ZONE, THE REMAINDER BEING WITHDRAWN AT THE TOP OF THE 